JPS61265499A - Heat transfer tube - Google Patents

Abstract

PURPOSE:To improve overall heat-transfer coefficient without increasing pressure loss in the tube by a method wherein the heat transfer tube is provided with a multitude of spiral recessed grooves on the inner surface there of and continuous or discontinuous wedge shape protuberances on the outer surface thereof with predetermined heights and pitches respectively. CONSTITUTION:The tube 1 is provided with a multitude of spiral protuberances 2 continuously or discontinuously on the outer surface thereof and a multitude of spiral grooves 3 on the inner surface thereof continuously. The protuberance 2 is formed so as to have the wedge shape section, the height (h0) of 0.1-8mm and the pitch P0 of 0.5-8mm. The groove 3 is formed so as to have a truncated triangular section, the depth of groove (h1) of 0.05-1.0mm and the pitch P1 of 0.2-10mm. According to this constitution, the overall heat-transfer coefficient between the inside and outside of the tube may be increased without increasing the pressure loss of heat medium in the tube, whereby the heat transfer characteristic of the heat exchanger may be improved.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to improvements in heat exchanger tubes, and in particular to improvements in the heat transfer rate between the refrigerant inside the tubes and the fluid outside the tubes without increasing the refrigerant pressure loss inside the tubes. It is.

Conventional technology A heat exchanger tube that boils or condenses a refrigerant such as Freon inside the tube and exchanges heat with a liquid outside the tube is made of a star-shaped extruded material inside a smooth tube (4) as shown in Figure 5. (5) An enlarged inner fin tube and a corrugated tube (6) shown in FIG. 6 are well known.

5 Problems to be Solved by the Invention In the above heat transfer tubes, when the heat transfer rate is increased compared to a smooth tube, the refrigerant flow resistance inside the tube increases and the pressure loss increases, and when the refrigerant flow resistance inside the tube is lowered, the heat transfer rate increases. A friend with flaws who doesn't improve much.

Means for Solving the Problems In view of this, the present invention has developed a heat transfer tube that can improve the heat transfer rate without significantly increasing the refrigerant pressure loss inside the tube. In a heat transfer tube in which a large number of spiral protrusions and a large number of spiral grooves are integrally provided on the inner surface of the tube, and the refrigerant is boiled or condensed within the tube to exchange heat with the fluid outside the tube, the depth of the groove on the inner surface of the tube is Sao 0.05~
1.0+m++, groove pitch 0.2-1.0mm,
The protrusions on the outer surface of the tube are continuous or discontinuous, and the cross section of the protrusions is wedge-shaped, the height of the protrusions is 0.1 to 8 m, and the protrusion pitch is 'i'.
o, 5 to 8 m.

That is, in the present invention, as shown in FIG. 1, a large number of spiral protrusions (2) are continuously or discontinuously formed on the outer surface of a tube (1).
As shown in FIG. 2, the protrusion (2) has a wedge-shaped cross section, and its height h0] is 0.1 to Bms and the pitch (po) is 0.5 to 8 gourds. The main groove (3) has a triangular or trapezoidal cross-sectional shape as shown in Figure 3 0) (B) and (C), and the groove depth is b+)'i-0.05 to 1.0.
The ms pitch (pi) is 0.2 to 1.0 m.

Function: As described above, the heat transfer tube of the present invention has a large number of spiral protrusions on the outer surface of the tube and a large number of spiral grooves on the inner surface of the tube, so that there is no increase in pressure loss between the refrigerant inside the tube and the fluid outside the tube. The height of the protrusion on the outer surface of the tube can be reduced to 0.
1 to 8 was pitch is limited to 0.5 to 8 m (1, However, if the height of the protrusions is less than 0.1 and the pitch exceeds 8 m, the outer surface of the tube will become close to a smooth surface and the heat passage will be reduced.) The effect of the present invention, which increases the ratio, cannot be obtained, and the height exceeds 8cm and the pitch is 0.
This is because if it is less than 5-, the gap between the protrusions becomes narrow and the height of the protrusions becomes high, so that the extratubular fluid enters between the protrusions and becomes difficult to flow, and the effect of increasing the heat transfer rate is lost.

It is preferable that the height and pitch of the projections be selected and determined within the above range depending on the conditions of the extraluminal fluid.

In addition, the depth of the groove on the inner surface of the tube was limited to 0.05 to 1.0 m, and the pitch was limited to 0.2 to 1.0 + m.
If the pitch is less than 0.05w and the pitch is less than 0.2m, the inner surface of the tube will be close to a smooth surface and the heat transfer rate will be improved. Because it is lost. It is desirable that the depth and pitch of the opening grooves be selected and determined within the above range depending on the conditions of the refrigerant in the pipe.

Further, it is desirable that the twist angle of the grooves on the inner surface of the tube be 16 to 35 degrees, and within this range, boiling and condensation of the refrigerant inside the tube are well balanced, and the heat transfer rate can be significantly improved.

Example (1) On the outer surface of a tube made of phosphorus-deoxidized copper with an outer diameter of 12.7 m and an inner diameter of 11.46 mm, a large number of spiral protrusions with a wedge-shaped cross section of 1.59 m in height were released at a pitch of 1.34 square meters, Depth 0.2 on the inner surface of the tube
The trapezoidal groove shown in Fig. 3 (b) of the simple is made with a helix angle of 18° +,
. The heat transfer rate ratio and the refrigerant pressure loss ratio in the tubes were measured for the heat transfer tubes of the present invention formed in multiple spiral shapes with a pitch Q of 53 mm. The result was an outer diameter of 15.88 mm made of copper phosphate,
Groove f with depth W=1.30■ on the circumferential surface of the pipe with wall thickness 0.8m+
A corrugated pipe formed spirally with a pitch of P c = 8 ttm and shown in Fig. 6, made of phosphorus-deoxidized copper and having an outer diameter of 15
．． An extruded aluminum material with 10 radially arranged fins is fitted into a smooth tube with an inner diameter of 88 mm and an inner diameter of 14.28 mm.
A comparison is shown in FIG. 4 (a), (b), and (c) with the inner fin tube shown in the figure and a smooth tube made of phosphorus-deoxidized copper with a diameter of 15.813+ m and an inner diameter of 14.28 m+a.

To measure the heat transfer rate ratio and refrigerant pressure loss ratio in the pipe, a counter-current heat exchanger was used, Freon R-22 was used as the refrigerant in the pipe, and water was used as the cooling water outside the pipe. Characteristics 1
It was shown as

Figure 4 (a) shows the relationship between the refrigerant flow rate due to in-pipe evaporation and the heat transfer rate ratio, Figure 4 (b) shows the relationship between the refrigerant flow rate and in-pipe pressure loss ratio due to in-pipe evaporation, and Figure 4 (c) shows the relationship between the refrigerant flow rate due to condensation inside the tube and the heat transfer rate ratio. In the figure, (a) is the characteristic of the heat transfer tube of the present invention, (b) is the characteristic of the corrugated tube, and (C) is the characteristic of the inner fin tube. characteristics,
(d) shows all the characteristics of a smooth tube. Note that the vertical axes in FIGS. 4(a) and 4(b) e→ are the ratios when the smooth tube characteristics (d) are taken as t-1.

As is clear from the figure, the heat exchanger tube (a) of the present invention has a refrigerant pressure loss ratio close to that of the smooth tube (d) of the other conventional heat exchanger tube ('b), and a much higher heat transfer rate ratio than that of the conventional heat exchanger tube ('b). It can be seen that the characteristics are far superior compared to heat exchanger tubes.

Example (2) Example (1) A shell-and-tube heat exchanger was assembled using four types of heat exchanger tubes, and the heat exchange performance was compared under the same conditions. The results are shown in Table 1.

Table 1 Smooth tube 11 Inner fin tube 1.4 1.3 Corrugated tube 1.3 1.4 Heat exchanger tube of the present invention 2.2 2.0 Table 1 compares the heat exchange capacity of smooth tubes assuming 1 It can be seen that the heat exchanger tube of the present invention is far superior to any of the conventional heat exchanger tubes.

Effects of the Invention According to the present invention, the heat transfer rate between the inside and outside of the pipe can be significantly improved without increasing the pressure loss of the refrigerant inside the pipe, and when used in a heat exchanger, the heat transfer characteristics can be completely improved, and the size of the equipment can be reduced. This has significant industrial effects such as making it possible to reduce weight and weight.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view of an example of the heat exchanger tube of the present invention, Fig. 2 is a side sectional view showing an example of the external protrusions of the heat exchanger tube of the present invention, and Fig. 3 (f) (b) (c). shows the shape of the inner groove of the heat exchanger tube of the present invention, (a) is a cross-sectional view of the triangular groove;
(b) and (c) are cross-sectional views of trapezoidal grooves, and Figure 4 (a), (b), and (c) show the measurement results of the passage rate ratio and in-pipe refrigerant pressure loss ratio of the heat exchanger tube of the present invention and those of the conventional heat exchanger tube. This shows a comparison: (a) is the refrigerant flow rate and heat transfer rate ratio in tube evaporation, (b) is the tube pressure loss ratio in tube evaporation, and f→ is the relationship diagram between the heat transfer rate ratio in tube condensation. This figure is a perspective view showing an example of a conventional inner fin tube for heat exchanger tubes, and FIG. 6 is a perspective view showing an example of a conventional corrugated tube for heat exchanger tubes. 1. Pipe 2. Protrusion 3, groove 4. Smooth tube 5, star-shaped extrusion material 6. Corrugated tube diagram 1
Fig. 2 Fig. 3 Fig. 4 (a) Reiku 1 (kg/h) Original text (spontaneous) March 27, 1986

Claims (1)

[Claims] A heat exchanger tube that has a large number of spiral protrusions on the outer surface of the tube and a large number of spiral grooves on the inner surface of the tube, and boils or condenses a refrigerant within the tube to exchange heat with a liquid outside the tube. The groove depth on the surface is 0.05~1.0mm, the groove pitch is 0.2~
1.0 mm, the protrusion on the outer surface of the tube is continuous or discontinuous, the cross section of the protrusion is wedge-shaped, and the height of the protrusion is 0.1 to 8 m.
m, a heat exchanger tube characterized in that the protrusion pitch is 0.5 to 8 mm.